function delta = yuzhi(chro_old,chro_new)
[m,n] = size(chro_old);
old_f1 = chro_old(:,n-3:n-2);
old_f2 = chro_old(:,n-1:n);
new_f1 = chro_new(:,n-3:n-2);
new_f2 = chro_new(:,n-1:n);
w1 = zeros(m,1);
w2 = zeros(m,1);
for i = 1:m
    w1(i) = jiaoji(old_f1(i,:),new_f1(i,:));
    w2(i) = jiaoji(old_f2(i,:),new_f2(i,:));
end
new_area = w1.*w2;

old_area = (old_f1(:,2) - old_f1(:,1)).*(old_f2(:,2) - old_f2(:,1));

delta = mean(abs(old_area-new_area));

end

